Systems and methods for drive pressure spontaneous ventilation

ABSTRACT

This disclosure describes systems and methods for providing drive pressure ventilation of a patient. The disclosure describes a novel breath type that provides a spontaneous breath type that allows for the calculation of drive pressure that does not require invasive monitoring, where drive pressure is the pressure applied to the lungs that causes them to inflate during mechanical ventilation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/586,077, filed Nov. 14, 2017, and claims priority to U.S.Provisional Application Ser. No. 62/725,490, filed Aug. 31, 2018, thecomplete disclosures of which are hereby incorporated herein byreference in their entireties.

INTRODUCTION

Medical ventilator systems have long been used to provide ventilatoryand supplemental oxygen support to patients. These ventilators typicallycomprise a source of pressurized gas, such air or oxygen, which isfluidly connected to the patient through a conduit or tubing. As eachpatient may require a different ventilation strategy, modern ventilatorscan be customized for the particular needs of an individual patient. Forexample, several different ventilator modes or settings have beencreated to provide better ventilation for patients in various differentscenarios.

Methods and Systems for Drive Pressure Spontaneous Ventilation

This disclosure describes systems and methods for providing drivepressure ventilation of a patient. The disclosure describes a novelbreath type that provides spontaneous ventilation that allows for thecalculation of drive pressure that does not require invasive monitoring.To accomplish this goal, the drive pressure (DP) breath type (alsoreferred to herein as drive pressure ventilation) briefly interrupts andsmoothly transitions from a base spontaneous breath subtype, into atemporary breath subtype in response to the detection of a condition. Assuch, ventilator systems and methods utilizing the DP breath type asdisclosed herein may adjust ventilator parameters and/or perform otheractions based on a monitored dynamic drive pressure.

In part, this disclosure describes a method for drive pressureventilation of a patient with a ventilator. The method includes:

-   -   ventilating the patient with the ventilator in a spontaneous        breath subtype;    -   non-invasively monitoring respiratory data of the patient with        at least one of a pressure sensor and a flow sensor operatively        coupled to at least one of a patient circuit or a pressure        generating system;    -   analyzing the respiratory data to detect a patient effort;    -   delivering inspiratory gas to the patient with the ventilator in        response to a detected patient effort;    -   determining an occurrence of a condition by the ventilator based        on information gathered by the ventilator,    -   in response to the condition, determining a percent support        setting for the PA breath subtype based on a target setting or        the respiratory data from the spontaneous breath subtype;    -   automatically and temporarily switching from the spontaneous        breath subtype into the PA breath subtype for at least three        breaths in response to calculating the percent support setting;    -   estimating a respiratory system compliance and a respiratory        system resistance of the patient during the PA breath subtype        based on the respiratory data;    -   returning to the spontaneous breath subtype after the at least        three breaths;    -   calculating a drive pressure of the patient during the        spontaneous breath subtype utilizing the respiratory system        compliance, the a respiratory system resistance, and the        respiratory data received after the return; and    -   displaying the drive pressure.        The spontaneous breath subtype does not include a proportional        assist (PA) breath subtype.

Yet another aspect of this disclosure describes a ventilator system fordelivering drive pressure ventilation to a patient. The ventilatorsystem includes a pressure generating system, a ventilation tubingsystem, one or more non-invasive sensors, a controller, and a display.The pressure generating system generates a flow of breathing gas. Theventilation tubing system includes a patient interface. The patientinterface connects the pressure generating system to the patient. Theone or more non-invasive sensors are operatively coupled to at least oneof the pressure generating system or the ventilation tubing system. Theone or more non-invasive sensors generate output indicative of at leastone of flow, volume or pressure. The controller collects and analyzesthe output to determine a condition. In response to the condition, thecontroller temporarily switches the ventilator system from a spontaneousbreath subtype into a proportional assist (PA) breath subtype for atleast one breath. The controller estimates a respiratory systemcompliance of the patient during the PA breath subtype based on theoutput collected during the PA breath subtype. Additionally, after theat least one breath, the controller switches the ventilator system fromthe PA breath subtype back to the spontaneous breath subtype. After areturn to the spontaneous breath subtype, the controller calculates adrive pressure of the patient based on the respiratory system complianceand the output after the return. The display displays the drivepressure.

The disclosure further describes a non-transitory computer-readablemedium having computer-executable instructions for performing a methodof ventilating a patient with a ventilator. The method including:

-   -   ventilating the patient with the ventilator in a spontaneous        breath subtype;    -   monitoring respiratory data of the patient with at least one of        a pressure sensor and a flow sensor operatively coupled to at        least one of a patient circuit or a pressure generating system;    -   analyzing the respiratory data to detect a patient effort;    -   delivering inspiratory gas to the patient with the ventilator in        response to a detected patient effort;    -   determining an occurrence of a condition by the ventilator based        on information gathered by the ventilator;    -   in response to the condition, automatically and temporarily        switching from the spontaneous breath subtype into the PA breath        subtype for at least three breaths;    -   estimating a respiratory system compliance and a respiratory        system resistance of the patient during the PA breath subtype        based on the respiratory data;    -   calculating a drive pressure of the patient during the        spontaneous breath subtype utilizing respiratory system        compliance, the respiratory system resistance, and the        respiratory data received during the spontaneous breath subtype;        and    -   performing an action based on the drive pressure.        The spontaneous breath subtype does not include a PA breath        subtype. A percent support setting for the PA breath subtype is        determined based on at least one of a target setting, a        non-invasively monitored flow, a non-invasively monitored        pressure, or a noninvasively monitor tidal volume during the        spontaneous breath subtype from at least one of the pressure        sensor and the flow sensor by the ventilator.

These and various other features as well as advantages whichcharacterize the systems and methods described herein will be apparentfrom a reading of the following detailed description and a review of theassociated drawings. Additional features are set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the technology. Thebenefits and features of the technology will be realized and attained bythe structure particularly pointed out in the written description andclaims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawing figures, which form a part of this application,are illustrative of embodiments of systems and methods described belowand are not meant to limit the scope of the invention in any manner,which scope shall be based on the claims appended hereto.

FIG. 1 is a schematic diagram illustrating an example of a ventilator inaccordance with aspects of the disclosure.

FIG. 2 is flow a diagram illustrating an example of a method forventilating a patient on a ventilator in a drive pressure breath type,in accordance with aspects of the invention.

FIG. 3 is a chart illustrating an example of a normalized respiratorymechanics plane in accordance with aspects of the disclosure.

FIG. 4 is a chart illustrating an example of a normalized respiratoryplane with provided patient trend line in accordance with aspects of thedisclosure.

FIG. 5 is a chart illustrating an example of a normalized respiratoryplane with provided boundaries in accordance with aspects of thedisclosure.

DETAILED DESCRIPTION

Although the techniques introduced above and discussed in detail belowmay be implemented for a variety of medical devices, the presentdisclosure will discuss the implementation of these techniques in thecontext of a medical ventilator for use in providing ventilation supportto a human patient. A person of skill in the art will understand thatthe technology described in the context of a medical ventilator forhuman patients could be adapted for use with other systems such asventilators for non-human patients and general gas transport systems.

Medical ventilators are used to provide a breathing gas to a patient whomay otherwise be unable to breathe sufficiently. In modern medicalfacilities, pressurized air and oxygen sources are often available fromwall outlets. Accordingly, ventilators may provide pressure regulatingvalves (or regulators) connected to centralized sources of pressurizedair and pressurized oxygen. The regulating valves function to regulateflow so that respiratory gas having a desired concentration of oxygen issupplied to the patient at desired pressures and rates. Ventilatorscapable of operating independently of external sources of pressurizedair are also available.

While operating a ventilator, it is desirable to control the percentageof oxygen in the gas supplied by the ventilator to the patient. Further,as each patient may require a different ventilation strategy, modernventilators can be customized for the particular needs of an individualpatient.

For the purposes of this disclosure, a “breath” refers to a single cycleof inspiration and exhalation delivered with the assistance of aventilator. The term “breath type” refers to some specific definition orset of rules dictating how the pressure and flow of respiratory gas iscontrolled by the ventilator during a breath.

A ventilation “mode”, on the other hand, is a set of rules controllinghow multiple subsequent breaths should be delivered. Modes may bemandatory, that is controlled by the ventilator, or spontaneous, that isthat allow a breath to be delivered or controlled upon detection of apatient's effort to inhale, exhale or both. For example, a simplemandatory mode of ventilation is to deliver one breath of a specifiedmandatory breath type at a clinician-selected respiratory rate (e.g.,one breath every 6 seconds). Until the mode is changed, ventilators willcontinue to provide breaths of the specified breath type as dictated bythe rules defining the mode. For example, breath types may be mandatorymode breath types (that is, the initiation and termination of the breathis made by the ventilator) or spontaneous mode breath types (whichrefers to breath types in which the breath is initiated and terminatedby the patient). Examples of breath types utilized in the spontaneousmode of ventilation include proportional assist (PA) breath type, volumesupport (VS) breath type, pressure support (PS) breath type, and etc.Examples of mandatory breath types include a volume control breath type,a pressure control breath type, and etc.

Positive pressure delivery during mechanical ventilation can beinjurious to the lung. Therefore, measurements and methods that wouldallow for minimizing the lung injury have been utilized by mechanicalventilators to reduce lung injuries. Previously, studies showed thatutilizing low tidal volume was likely to prevent ventilator-induced lunginjury (VILI). However, newer studies have shown that low tidal volumesonly increase the chance of patient survival (or reduce the likelihoodVILI) if this low tidal volume is associated with decreases in patientdrive pressure. Further, studies have shown that increases in patientdrive pressure, particularly above 15 cm of H₂O, are strongly associatedwith decreased patient survival rates. As such, patient drive pressuremay be a better mechanical ventilation parameter than tidal volume forsurvival prediction and/or ventilation control.

Patient drive is the pressure that is applied ‘inside the lungs’ causingthem to inflate. This ‘driving pressure’ is what the lungs are exposedto in order to inflate them against the compliance of the lung. For amechanically ventilated patient, the patient drive pressure can becalculated as the pressure above baseline pressure applied by theventilator at the patient wye (i.e., Pwye−Pend exp), minus the pressureto overcome the artificial airway (i.e., RTUBE*QLUNG), minus thepressure created by the respiratory muscles (i.e., Pmus). Accordingly,the equation for calculating drive pressure is listed below:Pdrive=Pwye−Pend exp−RTUBE QLUNG−Pmus,  (EQ #1)where:

Pdrive is patient drive pressure;

Pwye is pressure at the wye;

Pend exp is pressure at the end of exhalation;

RTUBE is the resistance of the endotracheal tube or tracheostomy tube;

QLUNG is lung flow; and

Pmus, is muscle pressure.

During mandatory modes of ventilation, the patient is sedated. As such,during mandatory modes of ventilation, the muscle pressure of thepatient is zero since the patient is passive. Accordingly, if aninspiratory pause is applied to the patient during the mandatory mode ofventilation, such that the pressure on either side of the artificialairway (endotracheal tube or tracheostomy tube) is the same, the lungflow (QLUNG) will be zero and the above Equation #1 simplifies to:Pdrive=Pwye−Pend exp,  (EQ #2).However, in order for the above equation to work, the patient must beventilated utilizing a mandatory mode of ventilation and the patientmust be passive (such as sedated). As such, several ventilators arecapable of calculating and displaying drive pressure during mandatorymodes of ventilation on a passive patient with use of an inspiratorypause. However, if the patient is not passive, then the ventilator, evenduring a mandatory mode of ventilation, is not capable of calculatingpatient drive pressure. During a spontaneous mode of ventilation, thepatient is not passive so the patient's muscle pressure variesthroughout each breath and patient drive pressure is, therefore, a muchmore difficult calculation. Currently, the only ventilators that arecapable of calculating drive pressure during a spontaneous mode ofventilation or during any mode of ventilation where the patient is notpassive, requires invasive monitoring techniques.

Accordingly, the current disclosure describes a drive pressure (DP)breath type for ventilating a patient. The DP breath type (also referredto herein as drive pressure ventilation) is a spontaneous breath typethat allows for the calculation of drive pressure that does not requireinvasive monitoring. To accomplish this goal, the DP breath type brieflyinterrupts and smoothly transitions from a base spontaneous breathsubtype into a temporary proportional assist (PA) breath subtype for apredetermined period in response to a condition and then smoothlytransitions back into the base spontaneous breath subtype. In someaspects, the DP breath type accomplishes the smooth transition bydetermining a percent support setting for the PA breath subtype based onthe target settings of the base spontaneous breath subtype and/or basedon non-invasively monitored/measured parameters. In other aspects, apredetermined percent support setting is utilized for the transition bythe DP breath type. As such, ventilator systems and methods utilizingthe DP breath type may adjust ventilator parameters and/or perform otheractions based on a monitored drive pressure.

FIG. 1 is a schematic diagram illustrating an example of a ventilator100 connected to a human patient 150. Ventilator 100 includes apneumatic system 102 (also referred to as a pressure generating system)for circulating breathing gases to and from patient 150 via theventilation tubing system 130, which couples the patient 150 to thepneumatic system 102 via an invasive (e.g., endotracheal tube, as shown)or a non-invasive (e.g., nasal mask) patient interface 180.

Ventilation tubing system 130 (or patient circuit) may be a two-limb(shown) or a one-limb circuit for carrying gases to and from the patient150. In a two-limb embodiment, a fitting, typically referred to as a“wye-fitting” 170, may be provided to couple a patient interface 180 (asshown, an endotracheal tube) to an inspiratory limb 132 and anexpiratory limb 134 of the ventilation tubing system 130.

Pneumatic system 102 may be configured in a variety of ways. In thepresent example, pneumatic system 102 includes an expiratory module 108coupled with the expiratory limb 134 and an inspiratory module 104coupled with the inspiratory limb 132. Compressor 106 or other source(s)of pressurized gases (e.g., air, oxygen, and/or helium) is coupled withinspiratory module 104 and the expiratory module 108 to provide a gassource for ventilatory support via inspiratory limb 132.

The inspiratory module 104 is configured to deliver gases to the patient150 according to prescribed ventilatory settings. In some embodiments,inspiratory module 104 is configured to provide ventilation according tovarious breath types, e.g., via a DP breath type, or via any othersuitable breath types.

The expiratory module 108 is configured to release gases from thepatient's lungs according to prescribed ventilatory settings.Specifically, expiratory module 108 is associated with and/or controlsan expiratory valve for releasing gases from the patient 150.

The ventilator 100 may also include one or more non-invasive sensors 107communicatively coupled to ventilator 100. Sensors are referred toherein as non-invasive when the sensors are located externally topatient. For example, sensors located in the wye₌fitting 170, in theexpiratory module 108, in the inspiratory module 104, or on thepatient's finger are all external to the patient and are non-invasive.Sensors are referred to herein as invasive when the sensors are locatedwithin the patient or placed inside the patient's body, such as sensorslocated in an endotracheal tube, near a patient diaphragm, or on anesophageal balloon. While invasive sensors can provide great patientdata or measurements, these sensors can often be hard to maintain orkeep properly positioned. For example, an esophageal balloon can easilybe knocked out of proper position in response to patient movement. Oncemoved, all of the data recorded from the sensors on the balloon areinaccurate. Further, if condensation or material corrupts the sensor andinterferes with accurate measurements, the invasive sensor has to beremoved from the body to service and/or clean it. Further, becauseinvasive sensors are located within the patient, they usually requirethe patient to be sedated or undergo a surgical procedure forimplantation or positioning adjustment. As such, invasive sensors areburdensome to the patient, hard to implant, hard to maintain, and hardto keep positioned when compared to non-invasive sensors. The embodimentof FIG. 1 illustrates a sensor 107 in pneumatic system 102.

Sensors 107 may communicate with various components of ventilator 100,e.g., pneumatic system 102, other sensors 107, processor 116, conditionmodule 117, drive pressure module 118, treatment module 119, and/or anyother suitable components and/or modules. In one embodiment, sensors 107generate output and send this output to pneumatic system 102, othersensors 107, processor 116, condition module 117, drive pressure module118, treatment module 119 and any other suitable components and/ormodules. Sensors 107 may employ any suitable sensory or derivativetechnique for monitoring one or more patient parameters or ventilatorparameters associated with the ventilation of a patient 150. Sensors 107may detect changes in patient parameters indicative of patienttriggering, for example. Sensors 107 may be placed in any suitablenon-invasive location, e.g., within the ventilatory circuitry (excludingan endotracheal tube) or other devices communicatively coupled to theventilator 100. Further, sensors 107 may be placed within theventilatory circuitry or within components or modules of ventilator 100.For example, sensors 107 may be coupled to the inspiratory and/orexpiratory modules for detecting changes in circuit pressure and/orflow. In other examples, sensors 107 may be affixed to the ventilatorytubing or may be embedded in the tubing itself. Additionally oralternatively, sensors 107 may be affixed or embedded in or nearwye-fitting 170 and/or in a non-invasive patient interface. Indeed, anynon-invasive sensory device useful for monitoring changes in measurableparameters during ventilatory treatment may be employed in accordancewith embodiments described herein. In some aspects, the ventilator 100does not utilize any invasive sensors or sensory devices.

As should be appreciated, with reference to the Equation of Motion,ventilatory parameters are highly interrelated and, according toembodiments, may be either directly or indirectly monitored. That is,parameters may be directly monitored by one or more sensors 107, asdescribed above, or may be indirectly monitored or estimated/calculatedusing a model, such as a model derived from the Equation of Motion:

$\begin{matrix}{{{Pmus} = {{Pwye} - {{Pend}\mspace{14mu}\exp} - {\left( {{RTUBE} + {Rrs}} \right){QLUNG}} - \frac{\int{QLUNGdt}}{Crs}}},} & {{EQ}\mspace{14mu}{\# 3}}\end{matrix}$where:

Rrs is respiratory system resistance;

Crs is respiratory system compliance; and

∫QLUNGdt is lung flow integrated over time.

The pneumatic system 102 may include a variety of other components,including mixing modules, valves, tubing, accumulators, filters, etc.Controller 110 is operatively coupled with pneumatic system 102, signalmeasurement and acquisition systems, and an operator interface 120 thatmay enable an operator to interact with the ventilator 100 (e.g., changeventilator settings, select operational modes, view monitoredparameters, etc.).

In one embodiment, the operator interface 120 of the ventilator 100includes a display 122 communicatively coupled to ventilator 100.Display 122 provides various input screens, for receiving clinicianinput, and various display screens, for presenting useful information tothe clinician. In one embodiment, the display 122 is configured toinclude a graphical user interface (GUI). The GUI may be an interactivedisplay, e.g., a touch-sensitive screen or otherwise, and may providevarious windows and elements for receiving input and interface commandoperations. Alternatively, other suitable means of communication withthe ventilator 100 may be provided, for instance by a wheel, keyboard,mouse, or other suitable interactive device. Thus, operator interface120 may accept commands and input through display 122. Display 122 mayalso provide useful information in the form of various ventilatory dataregarding the physical condition of a patient 150. The usefulinformation may be derived by the ventilator 100, based on datacollected by a processor 116, and the useful information may bedisplayed to the clinician in the form of graphs, wave representations,pie graphs, text, or other suitable forms of graphic display. Forexample, patient data may be displayed on the GUI and/or display 122.Additionally or alternatively, patient data may be communicated to aremote monitoring system coupled via any suitable means to theventilator 100. In one embodiment, the display 122 may display one ormore of an alert, a current drive pressure, a past drive pressure, adrive pressure graph, a recommendation, a drive pressure breach of athreshold, a ventilation parameter change, a current patient effort, adiaphragmatic pressure, a patient respiratory compliance, a patientrespiratory resistance, a desired drive pressure range, a triggersensitivity, a condition, a tidal volume, a flow, a pressure, a targetsetting, a breath type, a ventilation mode, and/or etc.

Controller 110 is a command and control computing devices and mayinclude memory 112, one or more processors 116, storage 114, and/orother components of the type commonly found in command and controlcomputing devices. Controller 110 may further include a condition module117, a drive pressure module 118, and/or a treatment module 119 asillustrated in FIG. 1. A module as used herein may also refer to acommand and control computing device. A module as used herein may referto memory, one or more processors, storage, and/or other components ofthe type commonly found in command and control computing devices. Inalternative embodiments, the condition module 117, the drive pressuremodule 118, and the treatment module 119 may be located in othercomponents of the ventilator 100, such as the pressure generating system102 (also known as the pneumatic system 102).

The memory 112 includes non-transitory, computer-readable storage mediumthat stores software that is executed by the processor 116 and whichcontrols the operation of the ventilator 100. In an embodiment, thememory 112 includes one or more solid-state storage devices such asflash memory chips. In an alternative embodiment, the memory 112 may bemass storage connected to the processor 116 through a mass storagecontroller (not shown) and a communications bus (not shown). Althoughthe description of computer-readable media contained herein refers to asolid-state storage, it should be appreciated by those skilled in theart that computer-readable storage media can be any availablenon-transitory medium that can be accessed by the processor 116. Thatis, computer-readable storage media includes non-transitory, volatileand non-volatile, removable and non-removable media implemented in anymethod or technology for storage of information such ascomputer-readable instructions, data structures, program modules orother data. For example, computer-readable storage media includes RAM,ROM, EPROM, EEPROM, flash memory or other solid state memory technology,CD-ROM, DVD, or other optical storage, magnetic cassettes, magnetictape, magnetic disk storage or other magnetic storage devices, or anyother medium which can be used to store the desired information andwhich can be accessed by the computer.

The inspiratory module 104 receives a selected DP breath type from thecontroller 110. The DP breath type utilizes a mix of two differentbreath types (referred to herein as breath subtypes) and smoothlytransitions between the two different breath types. The two differentbreath types utilized within the DP breath type are referred to hereinas a base breath subtype and a temporary breath subtype that istriggered upon the detection or occurrence of a condition. The basebreath subtype is any spontaneous breath type other than the PA breathtype, such as a PS or VS breath type. In some aspects, the basespontaneous breath subtype is predetermined for the DP breath type. Inother aspects, the base spontaneous breath subtype is selected by theclinician. Depending upon the base spontaneous breath subtype, otherinputs, such as a target setting, may be required from the clinician foroperating the DP breath type. A target setting as utilized herein refersto a setting that has to be input for a breath type or breath subtype tofunction or work. For example, if the base spontaneous breath subtype isa PS breath type, the ventilator 100 may require a target pressure inputfrom the clinician. For example, if the base spontaneous breath subtypeis a VS breath type, ventilator 100 may require a target tidal volumeinput from the clinician. However, other inputs, such as patientinterface type, ventilation tubing system size, PEEP levels, and/or etc.may also be required from the clinician for operating the DP breath typedepending upon the type of ventilator and/or the base spontaneous breathsubtype. The temporary breath subtype is a PA breath type. When the PAbreath type is being utilized as the temporary breath subtype during aDP breath type, the PA breath type is referred to herein a PA breathsubtype. As such, while the use of different breath types, such as PA,PS, VS are discussed herein, these breath types are not beingimplemented, but instead are being utilized as breath subtype or portionwithin the DP breath type. During the DP breath type, the controller 110sends instructions to the inspiratory module 104 and/or the expiratorymodule 108 for delivering the base spontaneous breath subtype while thecondition module 117 of the controller 110 monitors for a condition.

Initiation and execution of a DP breath type requires detection of aninspiratory trigger. In some aspects, a patient trigger is calculatedbased on a measured or monitored patient inspiration flow. Any suitabletype of triggering detection for determining a patient trigger may beutilized by the ventilator 100, such as nasal detection, diaphragmdetection, and/or brain signal detection. Further, the ventilator 100may detect patient triggering via a pressure-monitoring method, aflow-monitoring method, direct or indirect measurement of neuromuscularsignals, or any other suitable method. Sensors 107 suitable for thisdetection may include any suitable sensing device as known by a personof skill in the art for a ventilator.

According to an embodiment, a pressure-triggering method may involve theventilator 100 monitoring the circuit pressure, and detecting a slightdrop in circuit pressure. The slight drop in circuit pressure mayindicate that the patient's respiratory muscles are creating a slightnegative pressure that in turn generates a pressure gradient between thepatient's lungs and the airway opening in an effort to inspire. Theventilator 100 may interpret the slight drop in circuit pressure as apatient trigger and may consequently initiate inspiration by deliveringrespiratory gases.

Alternatively, the ventilator 100 may detect a flow-triggered event.Specifically, the ventilator 100 may monitor the circuit flow, asdescribed above. If the ventilator 100 detects a slight drop in the baseflow through the exhalation module during exhalation, this may indicate,again, that the patient 150 is attempting to inspire. In this case, theventilator 100 is detecting a drop in bias flow (or baseline flow)attributable to a slight redirection of gases into the patient's lungs(in response to a slightly negative pressure gradient as discussedabove). Bias flow refers to a constant flow existing in the circuitduring exhalation that enables the ventilator 100 to detect expiratoryflow changes and patient triggering.

In response to a detection of a patient trigger, the controller 110sends instruction to the inspiratory module 104 to deliver breathing gasto the patient based on the parameters of DP breath type.

During ventilation with the base spontaneous breath subtype, thecondition module 117 monitors input to determine the occurrence of oneor more conditions. In some aspects, the condition module 117 monitorsthe measurements from the non-invasive sensors. In other aspects, thecondition module 117 monitors other received ventilator data orcalculations to determine the occurrence of the condition. In someaspects, the condition may be any event that is indicative of a changein patient respiratory system compliance and/or patient respiratorysystem resistance, such as a predetermined pressure differential, volumedifferential, a tidal volume differential, a specific flow waveformshape, a specific volume waveform shape, a specific pressure waveformshape, a predetermined change in pressure, a predetermined change inflow, a predetermined change in tidal volume and/or etc. For example,the condition may be a change in non-invasively monitored flow,pressure, and/or of volume of at least 25%. In other aspects, thecondition is an expiration of a set period or predetermined number ofbreaths, since the last PA breath subtype switch or since the start ofthe last PA breath subtype. For example, the condition may be theexpiration of 30, 60, 90, or 120 minutes or the occurrence of 400, 300,or 200 breaths since the last temporary switch into the PA breathsubtype or the start of the last PA breath subtype. In other examples,the condition module 117 monitors for the following condition tooccur: 1) expiration of 1 hour since the last PA breath subtype; or 2) a25% change in one of non-invasively measured pressure, flow, or tidalvolume during the base spontaneous breath subtype. If the DP breath typewas just initialized, the conditions discussed above may be monitoredfrom the start of ventilation or the start of the DP breath type insteadof since the last temporary switch into the PA breath subtype or thestart of the last PA breath subtype. If the condition module 117 detectsa condition, the condition module 117 of the controller 110 determines apercent support setting and sends instructions to the pressuregenerating pneumatic system 102 to provide a short temporary switch intoa PA breath subtype utilizing the determined percent support setting.

In some aspects, the condition module 117 determines a percent supportsetting by utilizing a predetermined or preset percent support setting.In other aspects, the condition module 117 determines a percent supportsetting based on a target setting for the base spontaneous breathsubtype. For example, if the target pressure for the PS breath type is10 cm H₂O, then the condition module 117 will determine a percentsupporting setting to achieve approximately the same pressure level. Inanother example, if the target volume for a VS breath type is 400 ml,then the condition module 117 will determine a percent support settingto achieve approximately the same volume level. In other aspects, thepercent setting is determined by the condition module 117 based onoutputs from the non-invasive sensor. For example, if inspiratorypressure measurement is 9.8 cm H₂O from inspiratory pressure sensor,then the condition module 117 will determine a percent support settingto achieve approximately the same pressure level. In further aspects,the condition module 117 may utilize additional ventilator parameters orinputs to the target setting and/or the outputs from the non-invasivesensor to determine a percent support setting, such as mask type,patient circuit diameter, and etc.

The PA breath subtype is an effort-based breath type that dynamicallydetermines the amount of ventilatory support to deliver based on acontinuous estimation/calculation of patient effort and respiratorycharacteristics. Patient effort as discussed in the PA breath type isnot a muscle pressure (Pmus). In contrast, the patient effort during thePA breath type refers to resistive and elastic pressure drops. Theresulting dynamically generated profile is computed in real- orquasi-real-time and used by the ventilator as a set of points forcontrol of applicable parameters.

Initiation and execution of an effort-based breath type, such as PAbreath type or PA breath subtype, has two operation prerequisites: (1)detection of an inspiratory trigger; and (2) detection and measurementof an appreciable amount of patient respiratory effort to constitute asufficient reference above a ventilator's control signal error deadband.Advanced, sophisticated triggering technologies detect initiation ofinspiratory efforts efficiently. Patient effort is calculated based onmeasured patient inspiration flow. Patient effort is utilized tocalculate a target airway pressure for the inspiration. The deliveredairway pressure as used herein is the airway pressure measured at theventilator-patient interface. The target airway pressure is resistivepressure (Presistive) plus elastic pressure (Pelastic) plus positive endexhalation pressure (PEEP), where Presistive and Pelastic are scaled bythe percent support setting.

A PA breath type or subtype refers to a type of ventilation in which theventilator acts as an inspiratory amplifier that provides pressuresupport based on the patient's effort. Usually, the degree ofamplification (the “percent support setting”) during a PA breath type isset by an operator or clinician, for example as a percentage based onthe patient's effort. However, during the DP breath type, the conditionmodule 117 determines the percent support setting provided during the PAbreath subtype.

In one implementation of a PA breath subtype, the ventilator maycontinuously monitor the patient's instantaneous inspiratory flow andinstantaneous net lung volume, which are indicators of the patient'sinspiratory effort. These signals, together with ongoing estimates ofthe patient's lung compliance and lung/airway resistance and theEquation of Motion

$\left( {{Pmus} = {{Pwye} - {{Pend}\mspace{14mu}\exp} - {\left( {{RTUBE} + {Rrs}} \right){QLUNG}} - \frac{\int{QLUNGdt}}{Crs}}} \right),$allow the ventilator to estimate/calculate a patient effort and derivetherefrom a target airway pressure to provide the support that assiststhe patient's inspiratory muscles to the degree selected by the operatoras the percent support setting. In this equation, the patient effort isinspiratory muscle pressure and is negative. The percent support settingas determined by the condition module 117 divides the total work ofbreathing calculated between the patient and the ventilator.

Unlike other spontaneous breath subtypes, the PA breath subtype cancalculate compliance and resistance without having to utilize aninvasive sensor. As such, the PA breath subtype is a spontaneous breathtype that is able to calculate dynamic respiratory system compliance andrespiratory system resistance. In other spontaneous breath subtypes, aninvasive sensor located in an esophageal balloon is needed. However, asdiscussed above, an esophageal balloon can easily become dislodged ifthe patient moves affecting sensor accuracy, is highly invasive toimplant, and/or is uncomfortable for a spontaneously breathing patient.Due to the disruptive nature of the esophageal balloon, the esophagealballoon is rarely utilized during a spontaneous breath subtype.

Due to the unique configuration of the PA breath subtype, the PA breathsubtype is capable of determining a patient respiratory systemcompliance and/or resistance in an end exhalation hold of 300 ms or 0.3seconds, which will usually go unnoticed by a spontaneously breathingpatient. In a typical PA breath type, this 300 ms end expiratory hold isprovided intermittently at random. During the DP breath type, the 300 msend expiratory hold is provided in the first, second, third, or fourthbreath of the temporary PA breath subtype portion of the DP breath type.Any additional 300 ms holds are provided after a predetermined number ofbreaths or after a set time period during the PA breath subtype. Inother words, the PA breath subtype does not provide the 300 ms endexpiratory hold at random but instead at predetermined intervals. Assuch, the DP breath type is able to calculate patient respiratorycompliance and patient respiratory system resistance without having toutilize an invasive sensor measurement. The DP breath type utilizes thefollowing equation to determine patient respiratory system compliance:C _(RAW)=(V _(LUNG)/Pressure_delta).

The DP breath type utilizes the following equation to determine patientrespiratory system resistance:R _(RAW) =R _(RAW+ET) −R _(ET),where:

R_(RAW) is patient respiratory system resistance;

R_(RAW+ET) is the combined resistance of the patient respiratory systemand the endotracheal tube/tracheostomy tube resistance; and

R_(ET) is endotracheal tube/tracheostomy tube resistance.

R_(RAW+ET) is the difference in lung pressure and wye pressure dividedby the estimated lung flow. The lung pressure is based upon the lungpressure at the beginning of exhalation minus exhaled volume times theelastance. Wye pressure is estimated as the measured pressure inside theventilator compensated for inspiratory limb resistance.

During the PA breath subtype, the drive pressure module 118 calculatespatient respiratory resistance and/or compliance based on non-invasivesensor output. The condition module 117 provides the PA breath subtypefor at least one breath. In some aspects, the condition module 117provides the PA breath subtype for at least three breaths. In someaspects, the condition module 117 provides the PA breath subtype until apredetermined number of patient respiratory compliance and/or resistancemeasurements have been made by the ventilator 100. In some aspects, thecondition module 117 provides the PA breath subtype until at least twoor three patient respiratory compliance and/or resistance measurementshave been made by the ventilator 100. In other aspects, the conditionmodule 117 provides the PA breath subtype until at least one, two,three, four, or five patient respiratory compliance and/or resistancemeasurements have been made by the ventilator 100. The predeterminednumber of patient respiratory compliance and/or resistance measurementscan be completed in 1 breath, 2 breaths, 3 breaths, 5 breaths, 7breaths, 8 breaths, 10 breaths, 12 breaths, 15 breaths, 20 breaths, 25breaths or 30 breaths. In other aspects, a predetermined number ofpatient respiratory compliance and/or resistance measurements can becompleted by the condition module 117 in 4 to 12 breaths.

After the temporary PA breath subtype portion has been completed (e.g.,the predetermined number of patient respiratory compliance and/orresistance measurements have been made by the ventilator 100), thecondition module 117 switches the ventilation of the patient back to thepreviously utilized base spontaneous breath subtype.

After the return to the previously utilized base spontaneous breathsubtype, the drive pressure module 118 monitors respiratory data of thepatient, such as the non-invasive sensor output. In some aspects, thedrive pressure module 118 estimates a dynamic drive pressure waveform ofthe patient during the spontaneous breath subtype based on therespiratory data and the respiratory system compliance and/orcompliance. Next, the drive pressure module 118 calculates a drivepressure of the patient during the spontaneous breath subtype utilizingthe respiratory system compliance and/or the respiratory systemresistance, and the respiratory data. The drive pressure calculated bythe drive pressure module 118 can be dynamic and/or static.

In some aspects, equations (1) and (3) can be combined to get thefollowing drive pressure equation:Pdrive=Rrs QLUNG+1/Crs∫QLUNGdt,  EQ #4.If equation #4 above is evaluated at the end of the inspiratory phase,and QLUNG is assumed to be zero (e.g., at the transition point betweeninspiration and exhalation), the integral of QLUNG is the tidal volume,Vt. Based on these assumptions, a static drive pressure is calculated bythe drive pressure module 118 of control 110 by utilizing the followingequation:Pdrive=1/Crs Vt=Vt/Crs,  EQ #5.In further aspects, a dynamic drive pressure is calculated by the drivepressure module 118 of control 110 by utilizing the following equation:Pmus=Pwye−Pend exp−(RTUBE+Rrs)QLUNG−1/Crs∫QLUNGdt,  EQ #6where:

Pmus=respiratory muscle pressure;

Pwye=pressure at the patient wye;

Pend exp=pressure at the end of the expiratory phase;

RTUBE=resistance of the artificial airway;

Rrs=patient respiratory resistance;

QLUNG=lung flow; and

Crs=compliance of the respiratory system.

As can be seen from the above equations, at the end of the inspiratoryphase where QLUNG=0 and ∫QLUNGdt=tidal volume, dynamic and static drivepressure are the same. However, when the lung flow is non-zero, thedriving pressure includes a component related to the resistance of thepatient respiratory system. Under some conditions, this can result inthe maximum driving pressure being higher than the driving pressure atthe end of the inspiratory phase. In these situations, the use of thedriving pressure at the end of inspiration (or static drive pressure)may not fully represent the impact of the ventilator 100 on lung injury.As such, the dynamic drive pressure measurement is a better or moreaccurate measurement for determining and/or preventing lung injury thanthe static drive pressure measurement.

The drive pressure module 118 measures the drive pressure repeatedlythroughout a breath. In some aspects, the drive pressure module 118measures drive pressure every servo cycle, such as every 2 milliseconds,5 millisecond, or 10 milliseconds. The servo cycle is the amount of timerequired by the processor 116 or controller 110 of the ventilator 100 toperform a calculation in response to a received measured pressure orflow. In some aspects, the sensors 107 send output or measurements everyservo cycle.

The drive pressure module 118 communicates the drive pressure to othermodules, such as the treatment module 119 and condition module 117,controller 110, the pneumatic system 102, and/or the display 122.

The treatment module 119 performs an action in response to receiving thedrive pressure. The action may include generating a display of the drivepressure, evaluating the drive pressure, generating an alert based onthe drive pressure, providing a recommendation based on the drivepressure, and/or changing ventilator parameters based on the drivepressure. For example, the treatment module 119 may send instruction tothe display to display 122 a determined drive pressure. In otheraspects, the treatment module 119 may generate a graph of the drivepressure, such as a waveform or bar graph of the drive pressure. Forinstance, the treatment module 119 may generate a graph or waveform ofdrive pressure versus time.

In some aspects, the treatment module 119 evaluates the drive pressureby comparing the drive pressure to a threshold. If the treatment module119 determines that the drive pressure breaches the threshold, thetreatment module 119 performs an action in response to thisdetermination. As discussed above, the action may include a display ofthe drive pressure and/or the breach, generating an alert based on thebreach, providing a recommendation based on the breach, and/or changingventilator parameters based on the breach. If the treatment module 119determines that the drive pressure does not breach the threshold, thetreatment module 119 continues to evaluate the received drive pressuresfrom the drive pressure module 118. In further aspects, if the treatmentmodule 119 determines that the drive pressure does not breach thethreshold, the treatment module 119 may also provide a recommendation tothe clinician based on the drive pressure meeting the threshold.

The drive pressure threshold may be a drive pressure of 15 cm of H₂O orless, a drive pressure of 10 cm of H₂O or less, or a drive pressure of 5cm of H₂O to 15 cm of H₂O. This list is exemplary and is not meant to belimiting. Any suitable drive pressure range for optimal patientventilation may be utilized by the treatment module 119, controller 110,and/or ventilator 100. The threshold may be predetermined, selected bythe ventilator based on other patient information, or selected or inputby a clinician.

In response to a drive pressure or a breach of a threshold by the drivepressure, the treatment module 119 may generate an alert. The alert maybe a visual, audio, or any other type of sensory notification thatnotifies a clinician that the patient's drive pressure has breached apredetermined threshold. In response to a drive pressure meeting athreshold, or a breach of a threshold, the treatment module 119 mayprovide a recommendation. The recommendation may be changes toventilator parameters, such as target settings, other ventilatorsettings, changes in breath type, changes in breath subtype, and/orchanges in ventilator mode. For example, if the drive pressure exceeds athreshold, such as is greater than 15 cm of H₂O, the treatment module119 may recommend a decrease in tidal volume, a decrease in flow, adecrease in pressure, an increase in PEEP, and/or a decrease in PEEP totry and bring the drive pressure within the desired levels. For example,if the drive pressure exceeds a threshold, such as is less than 2 cm ofH₂O, the treatment module 119 may recommend an increase in tidal volume,an increase in flow, an increase in pressure, and/or a increase in PEEPbecause such changes may be beneficial for the patient and have no orvery low risk of causing lung injury. Alternatively, the treatmentmodule 119 may automatically modify the ventilation parameters listedabove based on drive pressure or the result of a comparison of drivepressure to a threshold. The ventilation parameter may include a targetsetting, oxygen percentage, rise time, trigger sensitivity, peak flowrate, peak inspiratory pressure, tidal volume, and/or PEEP. In someaspects, the treatment module 119 may adjust ventilation parameters tomaintain the drive pressure within a target range, such as thethreshold. An automatic change in ventilation parameter may be sent bytreatment module 119 to the display 122 or other modules to notify theclinician of the change.

As discussed above, method 200 illustrates a method for drive pressureventilation of a patient with a ventilator. Accordingly, method 200ventilates a patient with a DP breath type. Method 200 provides aspontaneous breath type that allows for the calculation of dynamic drivepressure and does not require invasive monitoring. To accomplish thisgoal, the method 200 briefly interrupts and smoothly transitions from abase spontaneous breath subtype, other than a PA breath subtype, intothe PA breath subtype in response to a condition and then smoothlytransitions back into the base spontaneous breath subtype when a patientrespiratory system compliance and/or resistance has been calculated.Method 200 accomplishes the smooth transition by determining a percentsupport setting for the PA breath subtype. As such, method 200 mayadjust ventilator parameters and/or perform other actions based on amonitored dynamic drive pressure.

As illustrated, method 200 includes a spontaneous ventilation operation201. During the spontaneous ventilation operation 201, the ventilatorventilates the patient utilizing a spontaneous breath subtype. Thespontaneous breath subtype is any spontaneous breath type other than aPA breath type.

As illustrated, method 200 includes a spontaneous collection operation202. During the spontaneous collection operation 202, the ventilatorcollects and analyzes non-invasive sensor output during the spontaneousbreath subtype. In other words, during spontaneous collection operation202, the ventilator non-invasively monitors respiratory data of thepatient. Non-invasive sensor output or respiratory data refers to theoutput or measurements generated by non-invasive sensors. As such, insome aspects, during spontaneous collection operation 202, theventilator collects flow rate, tidal volume, and/or pressuremeasurements from non-invasive sensors located in the ventilator 100and/or ventilation tubing system 130. In some aspects during spontaneouscollection operation 202, the ventilator 100 estimates a pressure orflow at the wye-fitting 170 based on an analysis of the non-invasivesensor output. In other aspects, other parameters are derived by theventilator 100 during spontaneous collection operation 202 based onanalysis of the of the non-invasive sensor output.

During spontaneous ventilation operation 201 and spontaneous collectionoperation 202, the ventilator analyzes the non-invasive sensor output orrespiratory data to detect a patient effort. During spontaneousventilation operation 201 and spontaneous collection operation 202, theventilator delivers inspiratory gas to the patient with the ventilatorin response to a detected patient effort. The inspiratory gas isdelivered according to the spontaneous breath subtype.

At DP operation 204, a drive pressure of the patient is calculated orestimated during the spontaneous breath subtype utilizing a calculatedor estimated compliance measurement and/or resistance measurementdetermined during the last PA breath subtype and the output from thesensors during the spontaneous breath subtype. The calculation and/orestimation of the compliance measurement and/or resistance measurementis discussed in more detail below and performed during analyze operation212 and compliance operation 214. In some aspects, the ventilator duringDP operation 204 may calculate or estimate the muscle pressure of thepatient during the spontaneous breath subtype based on the compliancemeasurement and/or resistance measurement. During DP operation 204, theventilator calculates or estimates a dynamic drive pressure. Forexample, as discussed above, the ventilator during DP operation 204 maycalculate or estimate the dynamic drive pressure by utilizing Equation#6 listed above. In some aspects, the ventilator during DP operation 204is also capable of calculating or estimating static drive pressure byutilizing Equation #5 listed above.

Method 200 also includes a determination operation 206. At determinationoperation 206, the ventilator determines if a condition occurred. Insome aspects, the ventilator during determination operation 206 monitorsthe non-invasive sensor output to determine if the condition hasoccurred. In other aspects, the ventilator during determinationoperation 206 monitors the number of delivered breath or the passage oftime to determine if a condition has occurred. If the ventilatordetermines that the condition occurred at determination operation 206,the ventilator selects to perform support setting operation 208. If theventilator determines that the condition did not occur duringdetermination operation 206, the ventilator selects to perform actionoperation 220. The condition may be the expiration of a predeterminedamount of time, the delivery of a predetermined number of breaths,and/or a change in one or more monitored parameters that indicates thata change in patient respiratory system compliance and/or resistance hasoccurred. In some aspects, the condition is a change in monitoredpressure, monitored tidal volume, or monitored flow of at least 25%. Inother aspects, the condition is expiration of 1 hour from the last useof the PA breath subtype without a change in monitored pressure,monitored tidal volume, or monitored flow of at least 25% since the lastPA breath subtype. In further aspects, the condition is the delivery of200 breaths from the last use of the PA breath subtype without a changein monitored pressure, monitored tidal volume, or monitored flow of atleast 25% since the last PA breath subtype.

As illustrated, method 200 includes support setting operation 208. Atsupport setting operation 208 the ventilator determines a percentsupport setting for a PA breath subtype. In some aspects, at supportsetting operation 208, the ventilator utilizes a predetermined supportsetting. In other aspects, at support setting operation 208 theventilator selects a support setting based on at least one of a targetsetting from the spontaneous breath subtype or the non-invasivelymeasured respiratory data collected during the spontaneous breathsubtype. In further aspects, the ventilator during support settingoperation 208 determines other settings for the PA breath subtype. Forexample, a PEEP level for the PA breath subtype may be set based on aPEEP level utilized in the spontaneous breath subtype.

Next, switch operation 210 is performed by the ventilator. At switchoperation 210 the ventilator automatically and temporarily switches fromthe spontaneous breath subtype into the PA breath subtype for at leastone breath utilizing the determined or calculated percent supportsetting. In some aspects, at switch operation 210 the ventilatorautomatically and temporarily switches from the spontaneous breathsubtype into the PA breath subtype for at least three breaths utilizingthe determined or calculated percent support setting. The PA breathsubtype is performed for at least one breath, at least two breaths, orat least three breaths. In some aspects, the PA breath subtype isdelivered by the ventilator during switch operation 210 until at leastone patient respiratory system compliance and/or resistance measurementhas been obtained. In some aspects, the PA breath subtype is deliveredby the ventilator during switch operation 210 until at least twodifferent patient respiratory system compliance and/or resistancemeasurements have been obtained. In some aspects, the PA breath subtypeis delivered by the ventilator during the switch operation 210 until 5,4, 3, or 2 patient respiratory system compliance and/or resistancemeasurements have been obtained. As such, the ventilator may deliverventilation utilizing the PA breath subtype for at most 4 breaths, 8breaths, 10 breaths, 12 breaths, 15 breaths, 20 breaths, 30 breaths, 40breaths, or 50 breaths.

Accordingly, method 200 also includes PA collect and analyze operation212. The ventilator during the PA collect and analyze operation 212,collects and analyzes the non-invasively measured respiratory dataduring the PA breath subtype. Next, a compliance operation 214 isperformed by the ventilator. During the compliance operation 214, theventilator calculates or estimates the patient respiratory systemcompliance and/or resistance based on the non-invasively measuredrespiratory data taken during the PA breath subtype during the PAcollect and analyze operation 212. If multiple patient respiratorysystem compliance and/or resistance measurements are taken by theventilator during compliance operation 214, the ventilator determines acompliance measurement and/or a resistance measurement based on thesemultiple measurements. For example, if multiple patient respiratorysystem compliance measurements are taken, the ventilator may average themeasurements or select the middle or last obtained measurement to beutilized as the PA breath subtype calculated compliance measurement foruse during DP operation 204.

Method 200 also includes a return operation 216. At return operation 216the ventilator switches from the PA breath subtype back to thepreviously utilized spontaneous breath subtype. As discussed above, theventilator returns the spontaneous breath subtype after a predeterminednumber of patient respiratory system compliance or resistancemeasurements have been obtained during the PA breath subtype, after apredetermined number of breaths, or after a predetermined amount oftime. Next, spontaneous ventilation operation 201 is performed again.

Method 200 also includes action operation 220. At action operation 220,the ventilator performs an action based on drive pressure. The actionmay include generating a display of the drive pressure, evaluating thedrive pressure, generating an alert based on the drive pressure,providing a recommendation based on the drive pressure, and/or changingventilator parameters based on the drive pressure. In some aspects, theventilator may generate a graph of the drive pressure for display duringaction operation 220, such as a waveform or bar graph of the drivepressure. In some aspects, the ventilator evaluates the drive pressureby comparing the drive pressure to threshold during action operation220. If the ventilator determines that the drive pressure breaches thethreshold during action operation 220, ventilator performs an action inresponse to this determination. As discussed above the action mayinclude a display of the drive pressure and/or the breach, generating analert based on the breach, providing a recommendation based on thebreach, and/or changing ventilator parameters based on the breach. Ifthe ventilator determines that the drive pressure does not breach thethreshold during action operation 220, the ventilator continues toevaluate the calculated or estimated drive pressure. In further aspects,if the ventilator during action operation 220 determines that the drivepressure does not breach the threshold, the ventilator may also providea recommendation to the clinician based on the drive pressure meetingthe threshold.

In response to a drive pressure or a breach of a threshold by the drivepressure, the ventilator may generate an alert during action operation220. In response to a drive pressure meeting a threshold, or a breach ofa threshold, the ventilator may provide a recommendation. Alternatively,the ventilator during action operation 220 may automatically modify theventilation parameters listed above based on drive pressure or theresult of a comparison of drive pressure to a threshold.

In some embodiments, a microprocessor-based ventilator that accesses acomputer-readable medium having computer-executable instructions forperforming the method of ventilating a patient with a medical ventilatoris disclosed. This method includes repeatedly performing the stepsdisclosed in method 200 above and/or as illustrated in FIG. 2. In someaspects, method 200 is performed by the ventilator 100 described abovewith reference to FIG. 1.

In another example, FIG. 3 is a chart illustrating a normalizedrespiratory mechanics plane (R-M Plane). FIG. 3 depicts the relationshipbetween tidal volume (ml) and distending pressure (ΔP in cmH2O).Distending pressure is calculated by subtracting the Positive EndExpiratory Pressure (PEEP) from Plateau Pressure (PPLAT), as illustratedby the X-axis of FIG. 3. In the context of patient ventilation, thefollowing equation would operationalize the relationship:V_(T)=ΔP*C_(L), where C_(L) represents the compliance (elasticity) ofthe patient lung-thorax system. The units of C_(L) for FIGS. 3 and 4 arevolume/pressure or ml/cmH₂O. Thus, if C_(L) is known, the volume (ml) isfound by multiplying C_(L) by ΔP. An examination of the equationV_(T)=ΔP*C_(L) reveals that C_(L) becomes a constant with the units ofV_(T)/ΔP. i.e., C_(L) is visualized as the positive slope of a lineoriginating at 0,0, rising linearly up and to the right (should aseparate slide be made). With a simple transformation of the units forthe Y-axis, volume/predicted body weight (PBW) (the volume units forlung protective ventilation (ml/kg) and likewise expressing C_(L) asC_(L)/kg provides the chart illustrated in FIG. 3. FIG. 3 assumes thefollowing:

1) The term ml/kg applied to all patients is valid and

2) The term C_(L)/kg applied to all patients is also valid.

As such, the following can be stated (where V_(L) is lung volume):

1) If V_(L)/kg and ΔP are known, C_(L)/kg=(V_(L)/kg)/ΔP;

2) If V_(L)/kg and C_(L)/kg are known, ΔP=(V_(L)/kg)/(C_(L)/kg); and

3) If ΔP and C_(L)/kg are known, V_(L)/kg=ΔP*C_(L)/kg.

Accordingly, any matched pair of coordinates for ml/kg and ΔP on FIG. 3locates a unique point on the R-M Plane and that point lies on a linewhose slope is ≈C_(L)/kg. Furthermore, all such matched coordinateswhose ratio is equivalent (≈) will also lie on that C_(L)/kg slope.Recognizing that valid estimates for ΔP and V_(L)/kg are available, theintersection of orthogonal projections of these two values identifies aprobable estimate of the patient's current C_(L)/kg. A current estimateof a patient's actual C_(L) is found by multiplying the normalized valueby the patient's estimated PBW.

Given the structure of the R-M Plane, it's now possible to indicate howthe patient's status can be monitored and identified, either by asoftware algorithm or by using boundary conditions set by the clinician.If the clinician were interested in maintaining lung-protectiveventilation, upper and lower, horizontal boundaries would alert whenV_(T)/kg were too low or too high. Ventilator notifications couldidentify key changes and suggest corrections. A patient with ARDS mightbe decompensating with ever worsening compliance. Boundary violationscould notify the clinician of this occurring.

In another aspect, a feature of the recurring points could be utilizedwith FIG. 3, to indicate the trajectory the patient's change asillustrated in FIG. 4. FIG. 4 is a chart illustrating a normalizedrespiratory mechanics plane with provided patient temporal status. Theconnection between sequential points would indicate rate of change and anotification could be provided by the ventilator to the clinician basedon this rate of change. In FIG. 4 the repeated values for V_(T)/kg, ΔPand C_(L)/kg are captured and processed every 5 minutes or so. At theend of each interval, software analyzes the patient's sensor data andindicates the patient's location on the R-M Plane. Identical sets ofvalues would produce equivalent points. However, as shown in FIG. 4, ifa new point differed by X from the last one, a new point whosestructure/identity would differ from the last one is plotted on thechart. In some aspects, each point is time stamped on the chart. Thethree vertical array points, illustrated in FIG. 4, indicate that theinsufflation pressure remained constant but the patient's C_(L) wasincreasing coincident with increasing V_(L). Given that the sequentialvalues for V_(T)/kg, ΔP and C_(L)/kg could change in any of severallogical trajectories, a temporal indicator on the R-M plane can apprisea clinician of the patient's status.

FIG. 5 is a chart illustrating a normalized respiratory mechanics planewith provided boundaries. Similar to FIG. 3, FIG. 5 depicts therelationship between tidal volume (ml) and distending pressure (ΔP incmH2O) and provides boundaries that show better and worse ventilationareas on the chart. In some aspects, FIG. 5 could be displayed at eachstart-up on request. FIG. 5 reinforces in the clinician's mind the areasof better or worse ventilation. In some aspects, once the patient's PBWis known, the depiction of FIG. 5 is converted to the given patient ordefaulted to the normalized patient as shown in FIG. 3.

In some embodiments, the ventilator system includes: means forventilating a patient with the ventilator in a spontaneous breathsubtype; means for non-invasively monitoring respiratory data of thepatient with at least one of a pressure sensor and a flow sensoroperatively coupled to at least one of a patient circuit or a pressuregenerating system; means for analyzing the respiratory data to detect apatient effort; means for delivering inspiratory gas to the patient withthe ventilator in response to a detected patient effort; means fordetermining an occurrence of a condition by the ventilator based oninformation gathered by the ventilator; in response to the condition,means for determining a percent support setting for a PA breath subtypebased on a target setting or the respiratory data from the spontaneousbreath subtype; means for automatically and temporarily switching fromthe spontaneous breath subtype into the PA breath subtype for at leastone breath in response to calculating the percent support setting; meansfor estimating a respiratory system compliance and/or respiratory systemresistance of the patient during the PA breath subtype based on therespiratory data; means for returning to the spontaneous breath subtypeafter the at least three breaths; means for calculating a drive pressureof the patient during the spontaneous breath subtype utilizing therespiratory system compliance and/or the respiratory system resistanceand the respiratory data; and means for performing an action based onthe drive pressure. The spontaneous breath subtype does not include aproportional assist (PA) breath type.

Those skilled in the art will recognize that the methods and systems ofthe present disclosure may be implemented in many manners and as suchare not to be limited by the foregoing exemplary embodiments andexamples. In other words, functional elements being performed by asingle or multiple components, in various combinations of hardware andsoftware or firmware, and individual functions, can be distributed amongsoftware applications at either the client or server level or both. Inthis regard, any number of the features of the different embodimentsdescribed herein may be combined into single or multiple embodiments,and alternate embodiments having fewer than or more than all of thefeatures herein described are possible. Functionality may also be, inwhole or in part, distributed among multiple components, in manners nowknown or to become known. Thus, myriad software/hardware/firmwarecombinations are possible in achieving the functions, features,interfaces and preferences described herein. Moreover, the scope of thepresent disclosure covers conventionally known manners for carrying outthe described features and functions and interfaces, and thosevariations and modifications that may be made to the hardware orsoftware firmware components described herein as would be understood bythose skilled in the art now and hereafter.

Numerous other changes may be made which will readily suggest themselvesto those skilled in the art and which are encompassed in the spirit ofthe disclosure and as defined in the appended claims. While variousembodiments have been described for purposes of this disclosure, variouschanges and modifications may be made which are well within the scope ofthe present invention. Numerous other changes may be made which willreadily suggest themselves to those skilled in the art and which areencompassed in the spirit of the disclosure and as defined in theappended claims.

What is claimed is:
 1. A ventilator system for delivering drive pressureventilation to a patient, the ventilator system comprising: a pressuregenerating system that generates a flow of breathing gas; a ventilationtubing system including a patient interface for connecting the pressuregenerating system to the patient; one or more non-invasive sensorsoperatively coupled to at least one of the pressure generating system orthe ventilation tubing system, wherein the one or more non-invasivesensors generate output indicative of at least one of flow, volume orpressure; a controller that collects and analyzes the output todetermine a condition, wherein the controller is configured to: inresponse to the condition, temporarily switch the ventilator system froma spontaneous breath subtype into a proportional assist (PA) breathsubtype for at least one breath; estimate a respiratory systemcompliance of the patient during the PA breath subtype based on theoutput collected during the PA breath subtype; after the at least onebreath, switch the ventilator system from the PA breath subtype back tothe spontaneous breath subtype; after a return to the spontaneous breathsubtype, calculate a drive pressure of the patient based on therespiratory system compliance and the output after the return, whereinthe drive pressure is a pressure represented in cmH₂O that is appliedwithin the patient's lungs to cause inflation; and a display fordisplaying the drive pressure.
 2. The ventilator system of claim 1,wherein the controller is further configured to: compare the drivepressure to a threshold to form a comparison; determine that the drivepressure breaches the threshold based on the comparison; and provide analert.
 3. The ventilator system of claim 2, wherein the controller isfurther configured to: adjust a ventilation parameter for the ventilatorsystem.
 4. The ventilator system of claim 3, wherein the ventilationparameter is at least one of oxygen percentage, rise time, triggersensitivity, peak flow rate, peak inspiratory pressure, tidal volume,PEEP, or a target setting.
 5. The ventilator system of claim 1, whereinthe controller is further configured to: utilize a predetermined percentsupport setting for the PA breath subtype.
 6. A non-transitorycomputer-readable medium having computer-executable instructions forperforming a method of ventilating a patient with a ventilator, themethod comprising: ventilating the patient with the ventilator in aspontaneous breath subtype, wherein the spontaneous breath subtype doesnot include a proportional assist (PA) breath subtype; monitoringrespiratory data of the patient with at least one of a pressure sensorand a flow sensor operatively coupled to at least one of a patientcircuit or a pressure generating system; analyzing the respiratory datato detect a patient effort; delivering inspiratory gas to the patientwith the ventilator in response to a detected patient effort;determining an occurrence of a condition by the ventilator based oninformation gathered by the ventilator; in response to the condition,automatically and temporarily switching from the spontaneous breathsubtype into the PA breath subtype for at least three breaths, wherein apercent support setting for the PA breath subtype is determined based onat least one of a target setting, a non-invasively monitored flow, anon-invasively monitored pressure, or a noninvasively monitor tidalvolume during the spontaneous breath subtype from at least one of thepressure sensor and the flow sensor; estimating a respiratory systemcompliance and a respiratory system resistance of the patient during thePA breath subtype based on the respiratory data; calculating a drivepressure of the patient during the spontaneous breath subtype utilizingrespiratory system compliance, the respiratory system resistance, andthe respiratory data received during the spontaneous breath subtype,wherein the drive pressure is a pressure represented in cmH₂O that isapplied within the patient's lungs to cause inflation; and performing anaction based on the drive pressure.
 7. The method of claim 6, whereinthe action includes providing a drive pressure alert.
 8. The method ofclaim 6, wherein the action includes providing a recommendation.